Selective MAC address learning

ABSTRACT

Methods, systems, and apparatus for selective MAC address learning are disclosed. In one aspect, multiple different packets are received by a telecommunications device. The multiple different packets include different source MAC addresses. For each of the multiple different packets, a distribution type is determined. The distribution type is one of a one-to-one distribution type or a one-to-many distribution type. Based on the determined distribution type of the particular packet, a forwarding table of the telecommunications device is selectively updated. When the particular packet has the one-to-many distribution type, a source MAC address that is included in the particular packet is not stored in the forwarding table. When the particular packet has the one-to-one distribution type, the source MAC address that is included in the particular packet is stored in the forwarding table.

BACKGROUND

This specification relates to MAC address learning.

Ethernet switching devices generally learn MAC addresses using aSource-Address-Learning method. For each received Ethernet packet, anEthernet switching device learns MAC address of packet source via sourceMAC address in the Ethernet packet. The Ethernet switching device canstore the learned source MAC address in its Content Addressable Memory(CAM) forwarding table.

SUMMARY

In general, one innovative aspect of the subject matter described inthis specification can be embodied in methods for selective MAC addresslearning by network devices with limited MAC address Content AddressableMemory (CAM) forwarding table spaces in Ethernet MAC-Switched Networks.One example computer-implemented method includes receiving, by atelecommunications device, multiple different packets that includedifferent source MAC addresses, determining a distribution type of eachof the multiple different packets, the distribution type being one of aone-to-one distribution type or a one-to-many distribution type, andselectively updating a forwarding table of the telecommunications devicebased on the determined distribution type of the particular packet. Theselectively updating comprises the following operations: not storing asource MAC address that is included in the particular packet when theparticular packet has the one-to-many distribution type, and storing thesource MAC address that is included in the particular packet when theparticular packet has the one-to-one distribution type.

These and other embodiments can each, optionally, include one or more ofthe following features. Receiving the multiple different packetscomprises receiving the multiple different packets that are transmittedover a same Virtual LAN (V-LAN). The telecommunications device is anOptical Network Unit (ONU). The telecommunications device is an OpticalLine Termination (OLT). Determining the distribution type of each of themultiple different packets comprises the following operations:identifying unicast packets that have known destination MAC addresses,and determining that the unicast packets are of the one-to-onedistribution type. Packets of the one-to-many distribution type includebroadcast packets and multicast packets. The forwarding table of thetelecommunications device is a Content Addressable Memory (CAM)forwarding table.

Particular embodiments of the subject matter described in thisspecification can be implemented so as to realize one or more of thefollowing advantages. The methods, devices, and/or systems described inthe present disclosure can selectively learn MAC addresses, by atelecommunications device, using a Source-Address-Learning method basedon a distribution type of each received packet. If the received packetis a unicast packet, source MAC address in the received packet can belearned (e.g., used to update a CAM forwarding table of thetelecommunications device). However, if the received packet is abroadcast packet or a multicast packet, the source MAC address in thereceived packet will not be learned (e.g., not used to update the CAMforwarding table of the telecommunications device). In doing so, MACaddresses that typically do not carry traffic for the telecommunicationsdevice (i.e., undesirable MAC addresses) will not be stored in the CAMforwarding table of the telecommunications device, thereby resulting inmore efficient use of a limited amount of memory available in thetelecommunications device. For example, in situations where thetelecommunications device has a limited CAM forwarding table space,desirable MAC addresses (i.e., MAC addresses that carry trafficspecifically addressed for delivery to the telecommunications device)stored in the CAM forwarding table will not be over-written byundesirable MAC addresses that typically do not carry traffic for thetelecommunications device (e.g., source MAC addresses inbroadcast/multicast packets that are note specifically addressed fordelivery to the telecommunications device). In addition, since the CAMforwarding table stores only desirable MAC addresses, the likelihood offlooding a unicast packet due to unknown destination MAC address in theCAM forwarding table will be reduced. As a result, allocated bandwidthof an Ethernet LAN (E-LAN) can be preserved from being flooded (e.g.,used up) with unicast packets, thereby making the allocated bandwidthavailable to carry assigned traffic, especially on E-LANs with manyhosts that generate significant broadcast/multicast traffic.

While some aspects of this disclosure refer to computer-implementedsoftware embodied on tangible media that processes and transforms data,some or all of the aspects may be computer-implemented methods orfurther included in respective systems or devices for performing thedescribed functionality. The details of one or more embodiments of thesubject matter described in this specification are set forth in theaccompanying drawings and the description below. Other features,aspects, and advantages of the subject matter will become apparent fromthe description, the drawings, and the claims.

DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram illustrating an example networking environmentfor selective MAC address learning.

FIG. 2 is a block diagram illustrating an example networking environmentfor an example telecommunications device to selectively update itsContent Addressable Memory (CAM) forwarding table.

FIG. 3 is a flow chart of an example process for selectively learningMAC addresses based on received packet distribution types.

Like reference numbers and designations in the various drawings indicatelike elements.

DETAILED DESCRIPTION

This document describes methods, systems, and apparatus for selectiveMAC address learning that is performed by a telecommunications device(e.g., an Optical Network Unit (ONU)). For example, a telecommunicationsdevice can use a Source-Address-Learning method to learn MAC addresses(e.g., store the MAC addresses in a forwarding table of thetelecommunications device) only from unicast packets, rather thanstoring MAC addresses for all communications packets. For example, MACaddresses in broadcast and/or multicast packets are not learned and/orstored in the forwarding table of the telecommunications device.Although this disclosure refers to optical telecommunications systemsfor purposes of example, the subject matter of this document can beapplied to other types of telecommunications systems or other systemsthat offer Ethernet LAN (E-LAN) service.

An Ethernet MAC-switched network can connect a large number of hosts(e.g., computers, Optical Network Terminals, business CPEs, xDSL modems,cable modems, residential gateways). When using aSource-Address-Learning method, each switching device in the EthernetMAC-switched network can learn MAC addresses of the hosts via source MACaddresses in received packets, and may require a large ContentAddressable Memory (CAM) forwarding table to learn (i.e., store)addresses of the large number of hosts. When a CAM forwarding table in aswitching device (e.g., an inexpensive switching device) is limited insize, the addresses of the large number of hosts cannot all be learned,and most of the addresses may remain unknown to the switching device. Inaddition, due to various protocols (e.g., ARP, ICMPv6) that usebroadcast and/or multicast packets which are flooded, the CAM forwardingtable may be routinely over-written with MAC addresses learned fromsource MAC addresses of broadcast and/or multicast packets from hostsfor which the switching device typically does not carry traffic (e.g.,undesirable MAC addresses). Furthermore, Ethernet packets with unknowndestination MAC addresses (e.g., destination MAC address not found inthe CAM forwarding table) are flooded (e.g., transmitted over allports). When there is a constant background broadcast and/or multicasttraffic in the network, the switching device may be continuouslyover-writing its CAM forward table with MAC addresses that typically donot carry traffic for the switching device (e.g., undesirable MACaddresses), and thereby flooding most (if not nearly all) traffic.Flooding unicast packets (e.g., transmitted unicast packets over allports) may reduce network capacity and affect allocated bandwidth inlarge-scale MAC-switched networks.

The disclosed subject matter addresses problems that arise when carrierEthernet E-LAN service (i.e., MAC-switched service) is offered via aPassive Optical Network (PON) (e.g., a Gigabit Passive Optical Network(GPON)) and/or Optical Network Units (ONUs) (also referred to as OpticalNetwork Terminals (ONTs)) at the network edge have limited CAM space. Inthe present disclosure, instead of learning all MAC addresses inreceived packets, a telecommunications device (e.g., a switching device,an ONU, an Optical Line Termination (OLT)) selectively learns MACaddresses in the received packets to utilize its limited CAM forwardingtable more efficiently. In the selective learning model, thetelecommunications device learns MAC Addresses bySource-Address-Learning and only learns source MAC addresses of unicastpackets. For example, when receiving unicast packets, thetelecommunications device learns source MAC addresses in the receivedunicast packets and store (or update) the learned source MAC addressesin its CAM forwarding table. However, when receiving broadcast and/ormulticast packets, the telecommunications device will not learn sourceMAC addresses in the received broadcast and/or multicast packets. As aresult, the CAM forwarding table will not be routinely over-written bybroadcast and/or multicast traffic. In doing so, the limited CAM spacemay be used to store MAC addresses only when unicast traffic is seenfrom the source, thereby improving the likelihood that MAC addressesthat carry traffic specifically addressed for delivery to thetelecommunications device are stored in its CAM forwarding table. As aresult, flooding a unicast packet due to unknown destination MAC addressin the CAM forwarding table may be reduced. In addition, allocatedbandwidth of an E-LAN can be preserved from flooded unicast packets.

FIG. 1 is a block diagram illustrating an example networking environment100 for selective MAC address learning. As illustrated in FIG. 1, theenvironment 100 includes an access node 102, an E-LAN 106 that providesEthernet service, and network 130. The access node 102 (e.g., TA5000)can serve as a first aggregation point to the network 130. In someimplementations, the environment 100 may include additional and/ordifferent components not shown in the block diagram, such as one or moreaccess nodes, another type of network that provides network services, ora combination of these and other technologies. In some implementations,components may also be omitted from the environment 100. As illustratedin FIG. 1, the E-LAN 106 is depicted as a single E-LAN, but may becomprised of more than one E-LANs without departing from the scope ofthis disclosure.

As illustrated, the access node 102 includes a switch component 104 andan OLT 108. The switch component 104 connects the OLT 108 to the network130. In some implementations, the switch component 104 forwards packetsfrom the network 130 to the E-LAN 106 and forwards packets from theE-LAN 106 to the network 130. In addition to the data plane forwardingfunctionality, the switch component 104 is also responsible forforwarding management traffic between the access node 102 and amanagement system in the network.

As illustrated, the E-LAN 106 includes the OLT 108 at a serviceprovider's central office (or other distribution point) and a number ofONUs 110, 112, and 114, which are located near end users. The OLT 108 iscoupled to the number of ONUs 110, 112, and 114, thereby forming apoint-to-multipoint Passive Optical Network (PON). For example, in thecase of Gigabit Passive Optical Network (GPON), a single OLT can have 8(or another number of) ports and each port can connect to 128 (oranother number of) different ONUs.

The OLT 108 learns the MAC addresses of each ONU (e.g., ONU 110, ONU112, ONU 114) and/or the residential gateways connected to those ONUsvia source MAC addresses in received packets. Similarly, it also learnsMAC addresses of the devices connected to the switch component upstreamin the network via source MAC addresses in received packets. In someimplementations, the OLT 108 may selectively learn MAC addresses basedon received packet distribution types (discussed in more detail below).When packets are received from the switch component 104 and are notdestined to the OLT 108, the OLT 108 may check the packets and its CAMforwarding table to determine how and where to forward the packets. Forexample, if receiving a broadcast packet 120, the OLT 108 may forwardthe broadcast packet 120 to all ONUs including ONU 110, ONU 112, and ONU114. If receiving a unicast packet 122 to ONU 110 or one or more devicesconnected to the ONU, the OLT 108 may forward the unicast packet 122 tothe ONU 110.

The ONUs (e.g., ONU 110, ONU 112, ONU 114) are generally located atnetwork edge and have limited CAM spaces. In normal operations, onlyseveral MAC addresses are needed in a CAM table of an ONU since trafficof the ONU is normally between the OLT and one or more devices connectedto the ONU. To prevent its limited CAM table from being over-written byundesirable MAC addresses, the ONU implements selective MAC addresslearning via source MAC addresses in received packets. For example, whenreceiving a unicast packet 122, ONU 110 may learn the source MAC addressthat is included in the received unicast packet 122, and store thelearned source MAC address in its CAM table. When receiving a broadcastpacket 120 (or a multicast packet not shown in FIG. 1), the ONU 110 willnot perform source MAC address learning on the received broadcast packet120. As a result, the CAM table of the ONU 110 will not be over-writtenby the source MAC address included in the received broadcast packet 120,which is generally undesirable to the ONU 110. ONU 112 and ONU 114 alsoreceive the broadcast packet 120 sent over the E-LAN 106. In thisexample, neither the ONU 112 nor the ONU 114 will perform source MACaddress learning on the received broadcast packet 120 because thebroadcast packet 120 is not a unicast packet. As a result, CAM tables ofthe ONU 112 and the ONU 114 will not be over-written by the source MACaddress included in the received broadcast packet 120.

The network 130 facilitates wireless or wireline communications betweenthe components of the environment 100 with any other local or remotecomputer, such as additional E-LANs, servers, or other devicescommunicably coupled to the network 130, including those not illustratedin FIG. 1. As illustrated in FIG. 1, the network 130 is depicted as asingle network, but may be comprised of more than one network withoutdeparting from the scope of this disclosure.

In some situations, one or more of the illustrated components may beimplemented, for example, as one or more cloud-based services oroperations. The network 130 may be all or a portion of a serviceprovider's access or aggregation network, an enterprise or securednetwork, or at least a portion of the network 130 may represent aconnection to the Internet, a public switched telephone network (PSTN),a data server, a video server, or additional or different networks. Insome implementations, a portion of the network 130 may be a virtualprivate network (VPN). Further, all or a portion of the network 130 cancomprise either a wireline or wireless link. Example wireless links mayinclude 802.11ac/ad/af/a/b/g/n, 802.20, WiMax, LTE, and/or any otherappropriate wireless link. In other words, the network 130 encompassesany internal or external network, networks, sub-network, or combinationthereof, operable to facilitate communications between various computingcomponents, inside and outside the environment 100. The network 130 maycommunicate, for example, Internet Protocol (IP) packets, Frame Relayframes, Asynchronous Transfer Mode (ATM) cells, voice, video, data, andother suitable information between network addresses. The network 130may also include one or more local area networks (LANs), radio accessnetworks (RANs), metropolitan area networks (MANs), wide area networks(WANs), all or a portion of the Internet, and/or any other communicationsystem or systems at one or more locations.

FIG. 2 is a block diagram illustrating an example networking environment200 for an example telecommunications device (i.e., ONU 110) toselectively update its Content Addressable Memory (CAM) forwardingtable. The environment 200 shown in FIG. 2 illustrates a simpleinteraction between the OLT 108 and the ONU 110 when the OLT 108forwards (or transmits) a broadcast packet 120 and a unicast packet 122to the ONU 110. In some implementations, the environment 200 may includeadditional and/or different components not shown in the block diagram.Components may also be omitted from the environment 200. The componentsillustrated in FIG. 2 may be similar to or different from thosedescribed in FIG. 1.

As illustrated in FIG. 2, the environment 200 includes the OLT 108 andthe ONU 110. The ONU 110 includes a receiver optical sub-assembly (ROSA)202 for receiving downstream data from the OLT 108, a processor 204, aCAM table 206, and a trash can 208 (e.g., a place to hold receivedbroadcast and multicast packets). In operation, the ROSA 202 receives anoptical signal as input, and outputs an electric signal.

As illustrated in FIG. 2, the ONU 110 includes a processor 204. Althoughillustrated as a single processor 204 in FIG. 2, two or more processorsmay be used according to particular needs, desires, or particularimplementations of the ONU 110. Each processor 204 may be a centralprocessing unit (CPU), an application-specific integrated circuit(ASIC), a field-programmable gate array (FPGA), or another suitablecomponent. Generally, the processor 204 executes instructions andmanipulates data to perform the operations of the ONU 110. Specifically,the processor 204 executes the selective source MAC address learningdescribed in the illustrated figures, including the operationsperforming the functionality associated with the ONU 110. For example,the processor 204 can determine whether a received packet is a unicastpacket, broadcast packet, or a multicast packet based on, for example,an identified destination IP address in the received packet. Inaddition, the processor 204 can determine the source MAC addressincluded in the received packet (e.g., identify the source MAC addressat some specific location of the received packet).

For purposes of example, assume that a broadcast packet 120 is receivedfrom the OLT 108, and that the processor 204 determines that thereceived packet is a broadcast packet (e.g., a packet having aone-to-many distribution type) based on, for example, a broadcast MAC/IPaddress identified in the broadcast packet 120. In this example, theprocessor 204 will not perform source MAC address learning for thebroadcast packet 120 because the packet is a broadcast packet. Afterprocessing the broadcast packet 120 (e.g., obtaining data in the payloadarea), the broadcast packet 120 is dropped, for example, in the trashcan 208.

In another example, assume that a unicast packet 122 is received fromthe OLT 108, and that the processor 204 determines that the receivedpacket is a unicast packet (e.g., a packet having a one-to-onedistribution type) based on, for example, a unicast MAC or IP addressidentified in the unicast packet 122. In this example, the processor 204will perform source MAC address learning for the unicast packet 122because the packet is a unicast packet rather than a broadcast ormulticast packet. For example, the processor 204 identifies the sourceMAC address in the unicast packet 122, and stores the source MAC addressin the CAM table 206 if the source MAC address has not been previously(e.g., is not currently) stored in the CAM table 206. In someimplementations, if the source MAC address is already in the CAM table206, no action is required to update the table.

FIG. 3 is a flow chart of an example process 300 for selectivelylearning MAC addresses based on received packet distribution types. Theexample process 300 can be performed, for example, by one or moretelecommunications devices, such as those described with reference toFIGS. 1 and 2 (e.g., OLT 108, ONU 110). The example process 300 can alsobe implemented as instructions stored on a non-transitory,computer-readable medium that, when executed by one or moretelecommunications devices, configures the one or moretelecommunications devices to perform and/or cause the one or moretelecommunications devices to perform the actions of the example process300.

Multiple different packets are received by a telecommunications device(305). The multiple different packets include different source MACaddresses. In some implementations, the multiple different packets aretransmitted over a same Virtual LAN (V-LAN) and received by thetelecommunications device over the V-LAN. In some implementations, thepackets are Ethernet packets. The telecommunications device can be anOptical Network Unit (ONU) or an Optical Line Termination (OLT) in aGigabit Passive Optical Network (GPON) offering carrier Ethernet LAN(E-LAN) service. This implementation equally applies to more advancedrecent 10G PONs as well and not limited to GPON. E-LAN is a special formof V-LAN (i.e., a point to multipoint V-LAN) and the E-LAN service isMAC-switched.

For each of the multiple different packets, a distribution type isdetermined (310). The distribution type is one of a one-to-onedistribution type or a one-to-many distribution type. For example, aunicast packet has a distribution type of one-to-one. A broadcast packetor a multicast packet has a distribution type of one-to-many. In someimplementations, a unicast packet with an unknown destination MACaddress may be flooded. In some implementations, the flooded unicastpacket still has a distribution type of one-to-one.

A determination is made whether the distribution type of the particularpacket is one-to-one or one-to-many (315). If the particular packet hasthe one-to-one distribution type (e.g., a unicast packet), a forwardingtable of the telecommunications device is updated (320). For example, asource MAC address that is included in the particular packet is storedin the forwarding table, for example, if not previously stored (e.g., ifnot currently found in the forwarding table).

A unicast packet with an unknown destination MAC address will be floodedon an E-LAN since the destination MAC address is unknown. In suchsituation, if the telecommunications device is the destination of theunicast packet, the telecommunications device will update its forwardingtable with the source MAC address that is included in the unicastpacket. If the telecommunications device is not the destination of theunicast packet, the telecommunications device will not update itsforwarding table with the source MAC address that is included in theunicast packet. In some implementations, the forwarding table of thetelecommunications device is a Content Addressable Memory (CAM)forwarding table.

If the particular packet has the one-to-many distribution type (e.g., abroadcast packet or a multicast packet), the forwarding table of thetelecommunications device is not updated (325). For example, the sourceMAC address that is included in a broadcast packet or a multicast packetwill not be stored in the forwarding table of the telecommunicationsdevice even when the source MAC address has not been previously storedin the forwarding table (e.g., is not currently found in the forwardingtable). In some implementations, the telecommunications device onlylearns source MAC addresses of unicast packets (e.g., only updates itsforwarding table with the source MAC addresses that are included in theunicast packets).

The example process 300 shown in FIG. 3 can be modified or reconfiguredto include additional, fewer, or different actions (not shown in FIG.3), which can be performed in the order shown or in a different order.For example, before 310, the telecommunications device identifiesunicast packets that have known destination MAC addresses. In addition,the telecommunications device determines that the unicast packets are ofthe one-to-one distribution type. In some implementations, one or moreof the actions shown in FIG. 3 can be repeated or iterated, for example,until a terminating condition is reached. In some implementations, oneor more of the individual actions shown in FIG. 3 can be executed asmultiple separate actions, or one or more subsets of the actions shownin FIG. 3 can be combined and executed as a single action. In someimplementations, one or more of the individual actions shown in FIG. 3may also be omitted from the example process 300.

While this specification contains many specific implementation details,these should not be construed as limitations on the scope of anyinventions or of what may be claimed, but rather as descriptions offeatures specific to particular embodiments of particular inventions.Certain features that are described in this specification, in thecontext of separate embodiments, can also be implemented in combinationor in a single embodiment. Conversely, various features that aredescribed in the context of a single embodiment can also be implementedin multiple embodiments, separately, or in any suitable subcombination.Moreover, although features may be described above as acting in certaincombinations and even initially claimed as such, one or more featuresfrom a claimed combination can, in some cases, be excised from thecombination, and the claimed combination may be directed to asubcombination or variation of a subcombination.

Thus, particular embodiments of the subject matter have been described.Other embodiments are within the scope of the following claims. In somecases, the actions recited in the claims can be performed in a differentorder and still achieve desirable results. In addition, the processesdepicted in the accompanying figures do not necessarily require theparticular order shown, or sequential order, to achieve desirableresults.

What is claimed is:
 1. A method comprising: receiving, by atelecommunications device, multiple different packets that includedifferent source MAC addresses; determining a distribution type of eachof the multiple different packets, wherein the distribution type is oneof a one-to-one distribution type or a one-to-many distribution type,and determined based on a destination address that is specified in eachof the multiple different packets; and selectively updating a forwardingtable of the telecommunications device based on the determineddistribution type of each particular packet, including: not storing asource MAC address that specifies a source of the particular packet whenthe particular packet has the one-to-many distribution type; and storingthe source MAC address that specifies the source of the particularpacket when the particular packet has (i) the one-to-one distributiontype and (ii) the destination address specifying that thetelecommunications device is a destination of the particular packet. 2.The method of claim 1, wherein receiving the multiple different packetscomprises receiving the multiple different packets that are transmittedover a same V-LAN.
 3. The method of claim 1, wherein thetelecommunications device is an Optical Network Unit (ONU).
 4. Themethod of claim 1, wherein the telecommunications device is an OpticalLine Termination (OLT).
 5. The method of claim 1, wherein determiningthe distribution type of each of the multiple different packetsincludes: identifying unicast packets that have known destination MACaddresses; and determining that the unicast packets are of theone-to-one distribution type.
 6. The method of claim 1, wherein packetsof the one-to-many distribution type include broadcast packets andmulticast packets.
 7. The method of claim 1, wherein the forwardingtable of the telecommunications device is a Content Addressable Memory(CAM) forwarding table.
 8. A telecommunications device, comprising: acommunications interface that communicatively couples thetelecommunications device with a plurality of network devices; a memorystructure storing machine executable instructions; and one or moreprocessors that execute the machine executable instructions and performoperations including: receiving multiple different packets that includedifferent source MAC addresses; determining a distribution type of eachof the multiple different packets, wherein the distribution type is oneof a one-to-one distribution type or a one-to-many distribution type,and determined based on a destination address that is specified in eachof the multiple different packets; and selectively updating a forwardingtable of the telecommunications device based on the determineddistribution type of each particular packet, including: not storing asource MAC address that specifies a source of the particular packet whenthe particular packet has the one-to-many distribution type; and storingthe source MAC address that specifies the source of the particularpacket when the particular packet has (i) the one-to-one distributiontype and (ii) the destination address specifying that thetelecommunications device is a destination of the particular packet. 9.The device of claim 8, wherein receiving the multiple different packetscomprises receiving the multiple different packets that are transmittedover a same V-LAN.
 10. The device of claim 8, wherein thetelecommunications device is an Optical Network Unit (ONU).
 11. Thedevice of claim 8, wherein the telecommunications device is an OpticalLine Termination (OLT).
 12. The device of claim 8, wherein determiningthe distribution type of each of the multiple different packetsincludes: identifying unicast packets that have known destination MACaddresses; and determining that the unicast packets are of theone-to-one distribution type.
 13. The device of claim 8, wherein packetsof the one-to-many distribution type include broadcast packets andmulticast packets.
 14. The device of claim 8, wherein the forwardingtable of the telecommunications device is a Content Addressable Memory(CAM) forwarding table.
 15. A system, comprising: a plurality of networkdevices, each network device configured to send packets to atelecommunications device; and the telecommunications device configuredto: receive multiple different packets that include different source MACaddresses; determine a distribution type of each of the multipledifferent packets, wherein the distribution type is one of a one-to-onedistribution type or a one-to-many distribution type, and determinedbased on a destination address that is specified in each of the multipledifferent packets; and selectively update a forwarding table of thetelecommunications device based on the determined distribution type ofeach particular packet, including: not storing a source MAC address thatspecifies a source of the particular packet when the particular packethas the one-to-many distribution type; and storing the source MACaddress that specifies the source of the particular packet when theparticular packet has (i) the one-to-one distribution type and (ii) thedestination address specifying that the telecommunications device is adestination of the particular packet.
 16. The system of claim 15,wherein receiving the multiple different packets comprises receiving themultiple different packets that are transmitted over a same V-LAN. 17.The system of claim 15, wherein the telecommunications device is anOptical Network Unit (ONU).
 18. The system of claim 15, wherein thetelecommunications device is an Optical Line Termination (OLT).
 19. Thesystem of claim 15, wherein determining the distribution type of each ofthe multiple different packets includes: identifying unicast packetsthat have known destination MAC addresses; and determining that theunicast packets are of the one-to-one distribution type.
 20. The systemof claim 15, wherein packets of the one-to-many distribution typeinclude broadcast packets and multicast packets.